(1) Field of the Invention
The present invention relates to a stereoscopic video display apparatus which enables viewers to view a stereoscopic video without wearing any special glasses.
(2) Description of the Related Art
Apparatuses configured to include parallax barriers or lenticular lenses (spectroscopes) arranged facing viewers of a display apparatus such as a liquid crystal panel, a PDP, and the like have been conventionally known as apparatuses which display stereoscopic videos without requiring the viewers to wear special glasses. Such an apparatus including such spectroscopes displays a stereoscopic video by horizontally dividing light from a left-eye image and a right-eye image displayed on a display panel.
FIG. 21 is a diagram illustrating the principle of a stereoscopic video display apparatus 91a using a parallax barrier 92 and not requiring any glasses.
In the diagram, 91 denotes a video display panel, and 92 denotes a parallax barrier part.
The video display panel 91 is made up of left-eye pixel sequences and right-eye pixel sequences arranged alternately in the vertical direction (the direction z shown) in the sheet of FIG. 21. Each of the left-eye pixel sequences is made up of left-eye pixels L, and each of the right-eye pixel sequences is made up of right-eye pixels R.
The parallax barrier 92 is formed to include slit-shaped openings 92a and light-shielding portions 92b arranged alternately and extend in the vertical direction.
It is to be noted that a left-eye video 93L made up of the left-eye pixels L and a right-eye video 93R made up of the right-eye pixels R includes binocular parallaxes which enable viewers to perceive these videos as if they are a single stereoscopic video.
A viewer 94 who wish to watch a stereoscopic video sets his/her head at a predetermined position 94Px (normal position). By doing so, a left-eye video 93L enters a left eye 94L via one of the openings 92a, and a right-eye video 93R enters a right eye 94R via another one of the openings 92a. Thereby, the viewer 94 can recognize these videos as a stereoscopic video.
At this time, the light of the right-eye video 93R is shielded by one of the light shielding portions 92b and does not enter the left eye 94L, and the light of the left-eye video 93L is shielded by another one of the light shielding portions 92b and does not enter the right eye 94R.
However, such a conventional stereoscopic video display apparatus 91a requires the viewer 94 to set the head position 94P of his/her head at the predetermined position 94Px. In other words, if the head position 94P is deviated from the predetermined position 94Px, the light of the right-eye video 93R enters the left eye 94L and the light of the left-eye video 93L enters the right eye 94R. This produces a problem (pseudo stereoscopy) of disabling the viewer 94 to perceive an excellent stereoscopic video.
For this reason, in order to watch an excellent stereoscopic video, the viewer 94 needs to find out the normal position 94Px which enables generation of such stereoscopic video and fix the head position 94P at the normal position 94Px.
In addition, if the head position is deviated from the normal position 94Px while the viewer is watching the stereoscopic video, the head position 94P needs to be moved to and set at the normal position 94Px.
A technique (Patent Reference 1: Japanese Patent Publication No. 3030243) has been conceived to improve the aforementioned technique. In the case where a head position 94P is at a position deviated from such a normal position 94Px which yields actual stereoscopy, the technique switches a left-eye image 93L and a right-eye image 93R depending on the current head position 94P, and thereby enables a viewer to watch a normal video at the current head position 94P deviated from the normal position 94Px. However, this method is applicable only in the case where the number of viewers is one.
The problem of pseudo stereoscopy which is produced depending on a head position arises not only when a pair of a left-eye parallax image and a right-eye parallax image is displayed, but also when three or more parallax images are displayed.
FIG. 22 is a diagram showing an example of displaying sets of four parallax images.
Images A, B, C, and D (parallax images 99a to 99d) correspond to the displayed parallax images.
The positions 9L (positions 9La, 9Lb, . . . ) denote the positions of viewers. The positions 9La, 9Lb, 9Lc, and 9Ld show the positions at which the parallax images A, B, C, and D can be viewed, respectively.
As shown in this diagram, the sets of parallax images 99a to 99d are sequentially displayed on a parallel surface 9LL parallel to a video display panel 1 at predetermined position intervals.
Thus, if a left eye 94L is currently positioned at a position (position 9Ld) which enables viewing of a parallax image 99d depending on a movement of the head position 94P (FIG. 21), the parallax image 99d enters the left eye 94L.
In this case, a right eye 94R is currently positioned at a position (position 9La: for example, the fifth position when counted from the leftmost position among the shown positions) which enables viewing of a parallax image 99a, and thus the parallax image 99a enters the right eye 94R.
In this way, pseudo stereoscopy is produced.
Furthermore, a crosstalk is also produced if the left eye 94L is in the middle of the position 9La and the position 9Lb and the right eye 94R is in the middle of the position 9Lb and the position 9Lc.
The use of the technique using plural sets of parallax images shown in FIG. 22 enables viewing by plural viewers. The following description is given of a case where the left eye 94L and the right eye 94R of one of the two viewers 94 are positioned at the position 9La and the position 9Lb, respectively. At this time, the left eye 94L and the right eye 94R of the other viewer 94 are positioned at the position 9Lc and the position 9Ld, respectively. This enables simultaneous viewing by both the viewers 94.
As mentioned earlier, pseudo stereoscopy is produced when such a technique is used. One of such techniques which reduce pseudo stereoscopy caused in the technique shown in FIG. 23A is an approach disclosed in Non-patent Reference 1 (“Multi-Observers Tracking Autostereoscopic Display Using Parallax Barrier (which is a translation of the title of a Japanese Paper)”, Bao Yue, The Journal of the Institute of Image Electronics Engineers of Japan, Vol. 32, No. 5, pp. 667 to 673, (2003)).
FIG. 23A is a diagram showing a conventional image display scheme (shown in Non-patent Reference 1) using sets of three parallax images (images a to c) for two viewers.
As shown in the diagram, the technique of Non-patent Reference 1 uses each of opening portions 1 in a parallax barrier part for each of the sets of three parallax images. Furthermore, Non-patent Reference 1 discloses a scheme which performs tracking of two viewers (viewer 9b1 and viewer 9b2) and thereby enables the two viewers to watch a stereoscopic video without causing pseudo stereoscopy.
FIG. 23B is a diagram showing a table of operations in the scheme in Non-patent Reference 1.
The scheme of Non-patent Reference 1 uses only sets of three parallax images (i, ii, and iii in FIG. 23B) as sets of three parallax images to be displayed at parallax image display positions (a, b, and c in FIG. 23A) to be displayed.
The following description is given of a case where the two viewers 94 (viewers 9b1 and 9b2) are in static states (see the first case “Both viewers are in static states” in line 2 in the table of FIG. 23B).
In this case, a parallax image ii and a parallax image iii are displayed for (enter) the left eye and the right eye of the viewer 1 (viewer 9b1) (see column 5 and 6 of the first case in FIG. 23B). In this case, a parallax image i and a parallax image ii are displayed for the left eye and the right eye of the viewer 2 (see column 7 and 8 of the first case in FIG. 23B).
In this way, images (parallax images) which enter corresponding ones of the eyes of the viewers are watched (the images are displayed at positions corresponding to the eyes and thus are perceived by the viewers).
Here, the viewpoint positions of the respective images (parallax images i, ii, and iii) are, for example, the positions of imaging apparatuses at the time when the imaging apparatuses captured the images.
For example, a stereoscopic video is appropriately perceived by a viewer 94 when the viewpoint position of the image perceived through the left eye 94L is at the left side of the viewpoint position of the image perceived through the right eye 94R.
In the case of the first case in the table of FIG. 23B, the positions of the left eye 94L and the right eye 94R of the first viewer 9b1 are the positions b and c in FIG. 23B. In this case, the positions of the left eye 94L and the right eye 94R of the second viewer 9b2 are the positions a and b in FIG. 23B.
In this case, images i, ii, and iii are displayed at the respective positions a, b, and c as shown in the above case.
In other words, the image i displayed at the position a is an image at a viewpoint position at the left side of the viewpoint of the image ii displayed at the position b. In other words, the image ii displayed at the position b is an image at a viewpoint position at the left side of the viewpoint of the image iii displayed at the position c.
When three parallax images (a, b, and c) are arranged in this way in the first case of the table of FIG. 23B, the viewpoint positions of the images perceived through left eyes 94L of the respective viewers are located at the left sides of the viewpoint positions of the images perceived through left eyes 94L of the respective viewers. Therefore, both of the first and second viewers 9b1 and 9b2 can appropriately perceive a stereoscopic video, in other words, can enjoy stereoscopic viewing.
Next, a description is given of a second case (in the table of FIG. 23B) where the first viewer 9b1 moves to the right (see a motion 9b1m in FIG. 23A) without being tracked. As shown in the first case in table of FIG. 23B, the first viewer 9b1 perceives the parallax image iii using the left eye 94L and the parallax image i using the right eye 94R when images are displayed (see the earlier description). In this case, the right and left images are perceived opposite by the first viewer 9b1 due to pseudo stereoscopy.
To prevent this, the images are displayed such that the first viewer 9b1 can perceive the parallax images i and ii using the left eye 94L and the right eye 94R respectively, and the second viewer 9b2 can perceive the parallax images ii and iii using the left eye 94L and the right eye 94R respectively.
In this way, even in the second case after the movement 9b1m in FIG. 23A is made, both of the two viewers can enjoy stereoscopic viewing.
Next, a description is given of a third case where the viewer 2 moves to the left (as shown in a movement 9b2m in FIG. 23A and see the table of FIG. 23B). It is possible to prevent occurrence of pseudo stereoscopy also in this case in a manner similar to the aforementioned manner.
In this case, the parallax images to be displayed are rearranged such that the first viewer 9b1 can perceive the parallax images i and ii through the left eye 94L and the right eye 94R respectively, and the second viewer 9b2 can perceive the parallax images ii and iii through the left eye 94L and the right eye 94R respectively.
In this way, even in the third case after the movement 9b2m in FIG. 23A is made, both of the two viewers can enjoy stereoscopic viewing.